In a DS-CDMA system data that is to be transmitted is first modulated into symbols. Then each symbol is spread using a spreading code where the spreading codes are orthogonal to each other. By this spreading several symbols can be transmitted simultaneously, and the sum of all spread symbols is a sequence of chips. If the spreading codes are orthogonal and if the radio channel is non-dispersive, there will be no interference between the symbols when the despreading is performed in the receiver. However, if the channel is dispersive, there will be interference between the symbols at the despreading even if the codes are orthogonal. This is because the codes are orthogonal only when they are time-aligned, and due to the time dispersiveness of the channel, several non-time-aligned copies of the transmitted signal arrive at the receiver at the same time.
A cyclic prefix is a number of samples or chips, in a DS-CDMA system, attached to the beginning of a block of a signal that is to be transmitted. The samples are copies of the last samples of the block.
By adding a cyclic prefix that is at least as long as the channel impulse response, the received signal appears to be a cyclic convolution of the original block, without inter-block interference. Cyclic convolution in time domain is equivalent to element-wise multiplication in frequency domain. Two advantages of having a cyclic prefix in the transmitted signal are:                In the received signal, the interference induced by a time-dispersive multi-path channel will only be intra-block interference, not inter-block interference.        A cyclic prefix facilitates frequency domain processing.        
However, a cyclic prefix cannot be used for mobile communication standards already in use, such as Wideband Code Division Multiple Access (WCDMA)/High Speed Packet Access (HSPA), since terminals and base stations already in use (legacy devices) are not equipped to handle a cyclic prefix.
US2007201408 discloses selecting either a first transport format or a second transport format to transmit information corresponding to an input symbol sequence. The transport formats fit information into a timeslot having a predetermined duration. Based upon the selected transport format, either the information is created from the input symbol sequence using the first transport format or is created from the input symbol sequence using the second transport format. Creating the information for transmission using the first transport format applies a spreading code to the input symbol sequence. The information for transmission is transmitted in a selected timeslot having the predetermined duration. Creating and transmitting the information using the first transport format causes the transmitted information to occupy a first frequency band. Creating and transmitting the information using the second transport format causes the transmitted information to occupy a second frequency band that partially overlaps the first frequency band. US2007201408 describes transmitting with WCDMA and Interleaved Frequency Division Multiple Access (IFDMA) with cyclic prefix in parallel in uplink (UL). The base station transmitted to is aware of the transmission format and equipped to handle it.